Hydroxyphosphonocarboxylic acids have been used as corrosion inhibitors in rust inhibition systems. For example, the use of such inhibitors, either alone or in combination with other inhibitors such as chromates, is discussed in U.S. Pat. Nos. 4,847,017; 4,052,160; 3,933,427; and 4,057,511.
A problem with the use of phosphonocarboxylic acids, including hydroxyphosphonocarboxylic acids, is that they are extremely acidic by nature. Further, these compounds tend to be corrosive and a potential hazard.
In addition, a further problem which has been encountered in preparing phosphonocarboxylic acid solutions is that some of the phosphonocarboxylic acid may be deactivated during the preparation of the solution and accordingly not available for use in the inhibition system.